It has been known that the polymerization reaction of isobutylene involves cationic polymerization. A polymerization method which begins with a protonic acid in the presence of a Lewis acid catalyst has been developed. As a method for efficiently effecting initiation reaction for polymerization there has been developed Inifer method which comprises the use of 1,4-bis(.alpha.-chloroisopropyl)benzene (p-dicumyl chloride (abbreviated as DCC)) terminated by chlorine connected to tertiary carbon or the like as a polymerization initiator (as disclosed in U.S. Pat. No. 4,276,394). It is considered that an aromatic compound terminated by chlorinated tertiary carbon is desirable for the formation of a highly active cation in the polymerization initiation point. In the Inifer method, the polymerization degree of product can be controlled by selecting the ratio of the initiator and the isobutylene monomer, making it possible to provide a molecular weight necessary for the accomplishment of physical properties depending on the purpose. In the polymerization reaction under the conditions of high reaction temperature, the growing reaction involves a chain transfer reaction that causes a rise in the number of polymers, occasionally making it difficult to predetermine a molecular weight. However, at temperatures as low as -100.degree. C. to -30.degree. C., a reactivity close to living polymerization is exhibited, inhibiting chain transfer reaction. This allows the number of polymers to be predetermined by the initiator.
One of the problems of the prior art Inifer method is a drop of the initiator efficiency due to indanylation as a side reaction caused by the use of p-DCC as an initiator. The molecular weight of the polymer as a product varies with the drop of the amount of the initiator due to the side reaction. Another problem is the widening of the distribution of the molecular weight of the polymer which affects the physical properties thereof. In order to solve these problems, a method has been proposed which comprises the use of additives such as electron donor (as disclosed in JP-A-2-245004 (The term "JP-A" as used herein means an "unexamined published Japanese patent application"), JP-A-1-318014, JP-A-3-174403).
In order to put an isobutylene polymer into practical use as a practical material, the isobutylene polymer can be cured by introducing a reactive functional group into molecule or terminal thereof to effect vulcanization or crosslinking. In particular, a use of a bifunctional initiator such as p-DCC causes both ends of the polymer chain to be terminated by chlorinated tertiary carbon to provide a sufficient reactivity. The resulting product is useful as a crosslinked polyisobutylene rubber. Such a polymer having a reactive functional group introduced into the terminals thereof is known as a telechelic polymer. In order to introduce vinyl group into the ends of the polymer, a method has been developed which comprises adding a non-conjugated diene represented by formula CH.sub.3 .dbd.CH(CH.sub.2).sub.n CH.dbd.CH.sub.2 (JP-A-4-103606). In this case, a use of 1,9-decadiene is disadvantageous in that it involves a side reaction to produce a low molecular compound at the same time with the introduction of vinyl group into the ends of the polymer. Such a low molecular impurity has a high content of vinyl group derived from decadiene. Therefore, even a small amount of such a low molecular impurity can cause a rise in the crosslinking density that has a great effect on the physical properties of the product.
As a method for introducing vinyl group into a polymer there is also known as a method which comprises the use of an allyltrimethyl silane.
The problems with the production of a telechelic polymer by utilizing the Inifer method for a living cationic polymerization of isobutylene involve the close relation of the conditions of the chemical reaction. In the cationic polymerization, it is important that carbocations are stably produced at the growth ends. The higher the dielectric constant of the reaction solvent is, the greater the rate of cationic polymerization becomes. A method has been known which comprises the use of a halogenated hydrocarbon such as dichloromethane or compound containing nitro group (as disclosed in JP-A-63-205304, JP-A-63-205305). As the method for effecting a polymerization reaction with a hydrocarbon solvent a method which comprises the use of hexane, pentane, butane, propane or the like has been known (JP-B-5-32409 (The term "JP-B" as used herein means an "examined Japanese patent publication")).
The isobutylene polymerization with a halogenated hydrocarbon solvent proceeds at a relatively high rate and generates a polymerization heat of about 13 kcal/mol. Under the conditions that the polymerization reaction is completed in a period of time as short as about 1 to 10 minutes, the polymerization reaction rapidly generates a heat. In particular, when the polymer is produced on a large scale, a problem arises how to remove the reaction heat and control the temperature.
One of the causes of the distribution of molecular weight of the polymer is considered to have something to do with the ratio of the initiation reaction to growth reaction. Indanylation reaction is considered to have something to do with the reactivity in which the growth ends attack an aromatic ring in the initiator itself. The side reaction derived from decadiene is considered to have a mechanism similar to cationic polymerization.
The cationic polymerization is effected at a relatively low temperature. Thus, the resulting polymer is occasionally deposited in a form of gel or solid. The deposit is liable to be attached to the reaction vessel, giving difficulty in operation. At the same time, an introduction of the functional group into the ends of the polymer must be effected by a solid-liquid phase reaction that can lower the reaction rate. In this respect, a proper reaction solvent in which the resulting polymer can be solved is preferably selected.